Sound device for stringed instruments



Sept. 30, .1930. F FRANKEL 1,777,260

'SOU ND DEVICE FOR STRINGED INSTRUMENTS Filed July 14. 1927 2Sheets-Sheet l /vv Nfole Sept. 30, 1930. F; FRANKEL 1,777,260

SOUND DEVICE FOR STHINGED INSTRUMENTS Filed July 14, 1927 2 Sheets-Sheet2 i 6' l iiurmg Patented Sept. 30, 1930 UNITED STATES I'D-IDOL! FBANKEL,OI STOCKHOLM, SWEDEN SOUND DEVICE FOR STRING ED INSTRUMENTS Applicationflled luly 14, 1921, Serial No. 205,738, and in Germany October-12,1986.-

Sound boards for stringed instruments, such as for instance pianos,piano-fortes and the like, have hitherto been made from a wooden plate(clean spruce), which hasbeen planed off to a thickness of about 10 mm.at the treble portion and of about 6 mm. at the base portion. Glued tothe said plate is a number of transverse, crookedly planed ribs adaptedto strengthen particularly the inner portions of the plate.

At the edge portions of the plate, the said ribs have been reduced fromtheir original thickness of about 30 mm. to athickness of about 4 mm.only along a length of about 150 mm. from the edges of the platen Forthe said reduced end portions of the ribs recesses have beenmade in therear frame, and the plate has been directly glued to the said frame inorder that the edges of the plate may be firmly secured and thus theplate be capable of takin up the stress from the string pressure, w ichhas to be carried wholly or to the greatest extent by the plate.

In order to increase the bearing capacity of the said plate,particularly at the middle portions thereof, the plate was carefullydried and contracted and then the somewhat curved ribs or lists wereglued on. When the plate was then subjected to the moisture of the airit swelled and made the previously curved lists still more curved, sothat the whole plate was curved. In such a state the plate was glued tothe frame of the instrument. However, the sounding capacity of such aplate was very limited, andv a powerful, singing and noble tone cannotbe obtained.

The present invention relates to a new sounding system for stringedinstruments, whereby the musical value of the instrument will beconsiderablyincreased.

- The sounding system according to the invention consists of a pluralityof vibration beams which are with their ends very firmly secured to theframe of the instrument and which are of such a construction andstrength as to be able to carry the bridges and the whole stringpressure or a part, preferably a considerable part thereof. The saidbeams may preferably consist of two or more parts glued to each other inthe longitudinal direcpreferably 15 or 20 mm., in order that they may besufiiciently strong and capable of being reliably secured to the frame-In some cases the beams maybe of equal thickness throughout theirlength, i. e. the ends thereof will not be reduced, or the ends may bethicker than the middle portion.

A'thin sounding or vibration plate may, if desired, be glued to the saidbeams, and. said plate may be made of such a size as not to reach to theframe of the instrument, in which case the beams have to carry the wholestrin pressure, the plate being wholly relieve from such pressure.However, the said plate .may,:if desired, extend to the frame of theinstrument, at some or more places and be glued thereto, so as to carrypart of the string pressure, said part being at most of the total stringpressure, while the resulting part (thus at least25% of the pressure)will be carried by the vibration beams. However, the total-stringpressure'may in this case preferably be divided in such way that thebeams take up about 60'to of said pressure, while theremaining 40 or20%, respectively,of the pressure will be carried by the vibrationplate.

In a sounding device according'to this invention, where the:vibrationbeams carry the main part of the string-pressure and where thesounding plate secured thereto constitutes merely an appendix adapted togive the tone a certain character, but where the vibration beams form apowerful connection with the frame of the gear, the conditions will besuch that the vibrations of the strings are transmitted through thebridges and the vibration plate to the vibration beams and extend alongsaid beams until they are resisted by the 95 frame of. the instrument.

If now the end portions of the vibration beams are strong and firmlysecured to the frame, a violent conflict will arise between thevibrating part of the beams and the se- W3 cured part thereof. Thelatter part does not permit the vibrations to pass further on butresists them and sends them back and thus increases the vibrations andprolongs the time thereof. It has also been proved that, fir'st when thevibrations are subjected to the resistance from the frame, they willbecome the capacity of intensifying the tone and giving it the rightcharacter.

' a somewhat modified sounding device. Fig. 7 3 is a sectional view online 3 3 of Fig.

3. Figs. 4 and 5 are transverse sections of sounding devices accordingto further modi-: fications.

Referring first to Figs. 1 and 2 of the drawing, (1 represents the rearframe of the instrument, to which is secured a number of vibration beamsb, the ends of which are reduced to about half the thickness of the beamproper, as visible from Fig. 2. As men-. tioned, the thickness of thesaid reduced ends ought to be at least mm., preferably about to mm., inorder to obtain the required steadiness. Applied to the fore side of thesaid beams 72 is a vibration plate 0, the edges of which are glued tothe beams b and which does not extend to the frame a, except at twodiagonally opposed corners, as shown in Fig. 1, the plate '0 being gluedto the frame a at said corners. If desired, the plate 0 may ex.- tend toand be glued to the frame a also at other places, so as to assist thebeams b in carrying the string pressures to a greater or less degree. Aspreviously mentioned, the plate 0 ought tocarry at most 7 5%- of thetotalstring pressure, or preferablynot more than of said pressure, theremaining and preferably greater part being carriedby the vibrationbeams Z). The plate a may, if desired, not at all extend to the frame a,

i. e. be wholly carried by the beams 6,.in

which case the latter will have to carry the whole string pressure.Inserted into the plate 0 are'vibration intensifying fillets orplat-bands f made from harder wood than the plate proper, the bridges dadaptedto carry thestrings'in the usual way being se-.

cured to saidfillets. By such means, the vibrations from the bridges tothe vibration beams b will be more powerful and transmitted in a moreconvenient manner, so that the sounding possibilities will be betterutilized. r

In the'form of embodiment shown in Fig. 8, the vibration platec issecured to the back of the beam system b. By such means a more powerfuland noble tone will be ob.-

t ained, inasmuch as the tone will be better the greater the distance isbetween the strings and the plate. Besides, the bridges (Z are in thiscase carried by transverse plat-bands 6 extending to the frame a andglued thereto so as to prevent displacing of the bridges d. As shown,the plate 0 does notat all extend to the framev a, the string pressurebeing wholly carried by the beams b which may be reduced at the ends andsecured to the frame by gluing in the manner shownin Fig. 2.,

According to the modification shown in Fig; 4, the vibration beam is ofthe same thickness throughout its length, the ends thereof, which aresecured into recesses in the frame a by gluing, being not at allreduced. The beam 6 consists in this case of two parts glued to eachother in the longi tudinal direction, as indicated by the line Z. Inthis. case the two parts may preferably consist of wood havingadifferent degree of hardness and elasticity.

In the modification shown-inFigh, the ends of the vibration beam 5 arethicker than the middle portion thereof, it being held in mind that thethickness of the said ends must not be less than hereinbefore set forth.

A beam system according to-the invention, particularly such a systemhaving a sounding plate, has a considerably better vibration capacitythan the ordinary' sounding boards. By the increase of the vibrationcapacity the tone will be intensified and thus morepowerful and noble. V

What 1 claimas new and desire to secure by Letters Patent of the UnitedStates of America is 7 a V 1. A stringed instrument comprising a frame,a sounding system carried by said frame and bridges for the strings ofthe instrument carried by said sounding system, said latter systemcomprising" a plurality of vibration beams secured at their ends to saidframe and serving to carry the string pressure or a considerable partthereof.

2. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter systemcomprising a plurality ofvibration beams secured at their ends to said frame and serving'to carrythe string pressure or a considerable part thereof, and a vibrationplate being secured to said vibration beams. Y

3. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and serving to carrythe string pres sure or a considerable part thereof, a vibration platebeing secured to said vibration beams and also to said frame so as toassist the said beams in carrying the string pressure.

4. A stringed instrument according to claim 3, characterized by thevibration plate carrying at most 75% of the string pressure.

5. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and serving to carrythe string pressure or a considerable part thereof, av

vibration plate being secured to said vibration beams at the rear sidethereof.

6. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the ill]- strument carriedby said sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and serving to carrythe string pressure or a considerable part thereof, a vibration platebeing secured with its edges to said vibration beams.

7. A stringed instrument according to claim 5, characterized by thebridges being secured to plat-bands connected to the frame of theinstrument.

8. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and serving tocarrythe string presframe, a soundig system carried by said frameandbridges for the strings of the instrument carried by said soundingsystem, said latter system comprising a plurality of vibration beamssecured at their ends to said frame and serving to carry the stringpressure or a considerable part thereof, said beams consisting each ofat least two longitudinal parts glued to each other when in a curvedstate.

10. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the in strument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends tosaid frame and serving to carrythe string pres- 11. A stringed 1 imtrumsntcomprising a frame, a soundinsystemcm'ied by said frameandbridges for the stain s of-the in strumentca-rried by said soun' ingsystem, said latter system comprising aplurality of vibration beams securedat their ends'to said frame andserving'tocarry thestrin pressure or a considerable. part thereo saidbeams being of about the same thickness throughout theirlength. a 5

12. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frameand serving to carrythe string pressure or a considerable part thereof, a vibration platebeing secured to said vibration beams, said beams being of about thesame thickness throughout their length.

13. A stringed instrument com rising a frame, a sounding system carrieby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and servin to carrythe string pressure ora considera 1e part thereof, said beams consistingeach of at least two longitudinal parts glued to each other when in acurved state and bein of about the same thickness throughout teirlength.

14. A stringed instrument comprising a A frame, a sounding systemcarried by said frame and bridges for the strings of the instrumentcarried by said sounding system, said latter system comprising aplurality of vibration beams secured at their ends to said frame andserving to carry the string pressure or a considerable part thereof, avibration plate being secured to said vibration beams, said beamsconsisting each of at least two longitudinal parts glued to each otherwhen in a curved state and being of about the same thickness throughouttheir length.

15. A stringed instrument comprising a frame, a sounding system carriedby said frame and bridges for the strings of the instrument carried bysaid sounding system, said latter system comprising a plurality ofvibration beams secured at their ends to said frame and serving to carrythe string pressure or a considerable part thereof, said beamsconsisting each of at least two longitudinal parts glued to each otherwhen in a curved state, said separate parts of the vibrationbeams-consisting'of wood having a different degree of hardness andelasticity. 16. A stringed instrument comprising a frame, a soundingsystem carried by said frame and bridges for the strings of theinstrument carried by said sounding system, said latter systemcomprising a plurality of vibration beams secured at their ends to saidframe and serving to carry the string pressure or a considerable partthereof, a vibration plate being secured to said vibration beams, saidbeams consisting each of at least two longitudinal partsglued to eachother when in a curved state, said separate parts of the vibration beamsconsisting of wood having a difierent degree of hardness and elasticity..1 V a, 1

In testimony whereof I affix my signature.

. FRIDOLF FRANKEL.

